A stereo imaging device is used to obtain a stereo image using a pair of cameras, which are placed at left and right sides. In a conventional stereo imaging device, in order to obtain a stereo image, the relative positions and attitudes of a pair of cameras are fixed. Moreover, in order to improve a stereoscopic function, an active-camera stereo imaging device with many degrees of freedom, which can change convergent movements and base-line lengths and can zoom and perform other functions, has been also developed.
If the relative-position relationship of a pair of cameras shifts, a stereo image cannot be produced. Therefore, various methods have been developed to calibrate the above. For example, what is disclosed in Patent Document 1 is designed to store in advance calibration data (calibration parameters) of an imaging device and use the data to calibrate a captured stereo image.
What is disclosed in Patent Document 2 is designed to extract characteristic points from a stereo image from a stereo imaging device and calculate a fundamental matrix (relative geometric information between cameras that make a pair) from the correspondence of the characteristics points to estimate a positional or rotating shift as to the relative positions of the cameras that form a pair.